missing some valid params

[henkpoldergraaf1]

In the last releases of OneSignal, there are some parameters added which are not yet includes in the valid params list for the postNotification method (https://github.com/dreamonkey/laravel-onesignal-rest-api/blob/master/src/OneSignalClient.php#L152)

Could you add the new params like 'android_channel_id' and others found in https://documentation.onesignal.com/reference
Or do you need a pull request for it?

Thanks,

Erik